Fine spherical powders, especially alloy or elemental metal powders can be made by high temperature processing. Such processes are described in U.S. Pat. Nos. 3,909,241, 3,974,245, 4,592,781, 4,715,878, 4,502,885, 4,711,660 and 4,711,661.
One of the problems that occurs in this processing, especially plasma processing, is that powder tends to build up in the vicinity of the nozzle and powder port. This build up continues until the powder/carrier gas stream is effected and powder is not effectively injected into the plasma flame. This causes poor melting efficiency, thus decreasing the conversion efficiency to spherical powder. This build up can continue until the powder port is covered over and no powder is being injected into the flame. When any of these adverse occurrences are noted, the plasma processing system must be shut down temporarily to clean off the powder port/plasma nozzle area in order to effectively operate again. The plasma processing system is then started up again with this cycle repeating.
It would be a significant advance in the art to assure that powder is being injected consistently well into the flame by virtue of there being no partial or full blockages. Also, it would be a significant advance in the art if the plasma processing system could operate virtually continuously by virtue of not having to be shut down in order to clear off the powder port/plasma nozzle in order to remove fine powder build up.